Hydraulic cushion



May 30, 1967 R. A. MADLAND 3,322,039 1 HYDRAULIC CUSHION Filed Jan. '7,1966 I-mi 2 INVENTOR ROLF A. MADLAND B jaw, km 'h/ ATTORNEYS UnitedStates Patent 3,322,039 HYDRAULIC CUSHION Rolf A. Madland, ArlingtonHeights, 111., assignor to 'Parker-Hannifin Corporation, Cleveland,Ohio, a corporation of Ohio Filed Jan. 7, 1966, Ser. No. 519,387 9Claims. (Cl. 91-405) This invention relates in general to new and usefulimprovements in hydraulic cylinder and piston art, and more particularlyseeks to provide a novel means for cushioning the travel of a pistonduring the terminal portion of its stroke in the cylinder in which itoperates.

An object of this invention is to provide in a cylinder and pistonstructure, novel means for cushioning a terminal portion of a pistonstroke and including a valve plunger having a groove therein movable outof registry with a fluid passage to first throttle and then trap fluidwhereby entrapped fluid serves to cushion terminal movement of thepiston, fluid pressure of trapped fluid on one end of said plunger beingat substantially the same pressure as that opposing the opposite end ofthe plunger by the fluid disposed in advance of the piston beingcushioned and which is engageable with said opposite plunger end.

Another object of this invention is to provide a novel piston travelcushioning means of the character stated including a plunger valve whichis shiftable by piston engagement and which is pressure balanced at itsopposite ends in the manner stated so that a compression spring engagedwith an outer end portion thereof is effective to return the plungerfrom its active fluid throttling and trapping positions to a projectedinoperative position in which its groove is placed to permit free fluidpassage.

Yet another object of this invention is to provide a double actingpressure cylinder having at each end thereof one of the novel plungermechanisms, thereby to provide a fluid cushioning at each associated endof the piston, during the terminal portion of the stroke of the piston.

With the above and other objects in view that will hereinafter appear,the nature of the invention will be more clearly understood by referenceto the following detailed description, the appended claims and theseveral views illustrated in the accompanying drawings.

In the drawings:

FIGURE 1 is a longitudinal sectional view illustrating the double actingpiston and cylinder of this invention, parts being shown in elevation.

FIGURE 2 is an enlarged fragmentary sectional view illustratin the novelcushioning mechanism of this invention in its operative position.

FIGURE 3 is a fragmentary vertical cross-sectional view taken on theline 33 of FIGURE 2.

Referring now to the drawings in detail, reference is first made toFIGURE 1 wherein there is illustrated a pressure cylinder 5 having apiston 6 mounted for reciprocation therein, the piston 6 having a pistonrod 7 secured centrally thereof by a nut 8 fastened onto a fitted end 19of the rod 7. The other end of the piston rod 7 extends longitudinallyof the cylinder 5 and through an end wall or closure head 11. Anotherend wall or closure head 12 is mounted on the other end of the cylinderand has a projection or aperture mounting ear 9 thereon for pivotalengagement with an anchoring means or connection member (not shown). Theend wall members 11, 12 are secured to the cylinder 5 by groove welds13, or by any other appropriate means. Inlet and exhaust ports 14 and 15are provided, and in this illustration are shown secured to the outersurface of the cylinder 5, as by fillet welds 16, or any other approvedmeans. With the exception of the mounting ear 9 at- 3 ,3ZZ,3 9 PatentedMay 30, 1967 ice tached to the end wall 12, and a bore 17 in the endwall 11 to receive the piston rod 7, the end walls 11 and 12 are ofsubstantially identical construction. Therefore, only a single end walland its components will be described in detail.

The end wall 12 has an outer peripheral shoulder portion 18 engaging anend of the cylinder 5 and a recess to receive the weld 13. Spacedinwardly of the shoulder 18 is a peripheral groove 19 extending entirelyaround the outer surface of the end wall 12 but at a point spacedlongitudinally inwardly from the end of the cylinder 5. The groove 19communicates with the inner surface 20 of the port 14 through anaperture 21 extending through the wall of the cylinder 5. Another groove22 is positioned longitudinally inwardly of the groove 19 of the wall 12and is adapted to receive a sealing ring 23 effective to prevent leakageof fluid outwardly about the exterior of the reduced diameter portion 24of the end wall telescoped into the cylinder. The inwardly directedsurface 25 of the end wall 12 is presented to serve as an abutment forthe opposing face 56 of the piston 6.

A chamber 26 is formed as a central depression in the end wall 12 andcommunicates with the previously mentioned groove 19 by means of aradial bore or passageway 27 extending outwardly across or intersectinga longitudinal bore 28, thereby paralleling the axis of the end 'wall 12and cylinder 5. The bore 27 opens outwardly into the groove 19 and theport 14. The bore 28 extending outwardly of the cross bore or duct 27opens into a counterbore 31, said counterbore 31 being internallythreaded at 32 and provided at its outer extremity with a chamfer 33.The chamfer is adapted to receive an O-ring seal 34 and opens into afurther counterbore 35 adapted to receive a head 36 on a bore closureplug member 37. The plug member 37 is threaded into the tapped hole 32,compressing the O-ring seal 34 between the chamfer 33 and the groovedwall portion 39 of the plug 37 when the head 35 of the plug 37 issecured against the outwardly presented surface 40 of the counterbore 35. The plug 37 has a central bore 41 in which to receive a compressionspring 43.

A plunger 44 is slidably mounted in the bore 28 and is substantiallyaligned with the bore 41 in the plug 37. The spring 43 is disposed toabut against the end surface 45 of the plunger 44 and bias the plunger44 in a direction toward the interior of the cylinder 5. The plunger 44has an axial bore 46 and an annular groove 47 disposed about thisperiphery. The groove 47 is defined in part by a cut-01f edge 49 and isadapted to be aligned with the bore 27 when the plunger is in theinoperative or spring projected position shown at the right in FIGURE 1.Another groove 48 is provided in the periphery of the plunger 44adjacent the outer end 45 thereof, and is adapted to receive a snap ring50. The snap ring 51! is positioned to be engageable with the abutmentwall 51 to limit the inward travel of the plunger 44 in response to theforce exerted by the spring 43 in which extreme inward position theplunger groove 47 is placed to align with the bore 27 as shown at theright in FIGURE 1. The space defined exteriorly of the outer end of theplunger 44 by the counterbore 31 in the end wall 12, the

abutment surface 51, the bore 41 and the inner surface 42 of the plug 37defines a chamber 52.

When the plunger 44 is in the last-mentioned extreme inward orinoperative position, fluid from the chamber 26 is in communication withthe bore 27, the groove 47 of the plunger 44, the aperture 21 of thecylinder 5, and the port 14. Fluid from the chamber 52 is incommunication through the center bore 46 of the plunger 44, with a portor groove 55 extending radially outwardly across the inner end surface54 of the plunger 44, and with the interior of the chamber 26 and thefluid therein.

As a high pressure fluid acting against the surface 53 of the piston 6drives the piston toward the terminal portion of its stroke, the pistoncontacts the inner end surface 54 of the plunger 44 and moves theplunger longitudinally against the force exerted by the spring 43. Thegroove 47 in the plunger 44 then begins to move out of registry with thebore 27, thereby causing a throttling of the fluid attempting to passout through the bore 27. In response to further longitudinal movement ofthe piston 6, the edge 49 of the plunger groove 47 passes the bore 27,thereby causing the outer portion of the bore 27, the cylinder portaperture 21 and the bore 14 to be out of communication with the fluidthus trapped in the chamber 52,.the bore 46 and the chamber 26, andfurther longitudinal movement of the piston 6 toward the end wall 12 isopposed and cushioned by said trapped fluid. Because all of the fluid inthis trapped or closed system is at the same pressure for any givenposition of the piston 6 after the groove 47 of the plunger 44 moves outof communication with the bore 27, the fluid pressure on opposite endsurfaces 45 and 54 of the plunger is equal. This closed fluid pressuresystem acts as a cushion on the surface 56 of the piston 6, therebyretarding the velocity of the piston 6 in the terminal portion of itsstroke. It will be apparent by reference to FIGURE 2 that the plungerbore 46 and cross groove 55 will permit restricted escape of fluids fromthe entrapment chamber 52 as the piston surface 56 comes against theplunger 44 and forces it from its projected position shown at the rightin FIGURE 1 toward the full cushion effected position shown in FIG- URE'2.

Also, because the ressure on opposite end surfaces 45 and 54 of thelunger 44 is equal, the force of the Spring 43 against the surface 45 ofthe plunger 44 is the only substantial force acting upon the plunger 44to return the plunger 44 to its inoperative or inwardly projectedposition, and as the high pressure is withdrawn from the fluid actingupon the face 53 of the piston 6, the spring 43 is effective to move theplunger 44 longitudinally so that the groove 47 of the plunger 44 isagain brought into communication with the bore 27 of the end wall 12 asshown at the right in FIGURE 1. Pressurized fluid may then be appliedthrough the port 14, through the bore 27,

and against the face 56 of the piston 6, to drive the piston toward theend wall 11 in the same manner as hereindescribed for the movement ofthe piston toward the end wall 12, in the usual manner of a doubleacting cylinder. Although only a preferred embodiment of theinventionhas been illustrated and described herein, it is to be 1 understood thatmodifications may be made in the disclosed structures without departingfrom the spirit and scope of this invention as defined in the appendedclaims.

What is claimed is: 1. A pressure cylinder having end closures, pressurfluid inlet and outlet porting at the ends thereof and a pistonreciprocable therein between said closures, and a terminal strokecushioning means in at least one of said closures for cushioningterminal stroke movement of the piston theretoward, said one closurehaving a pressure chamber therein in which to receive pressure fluid inadvance of the piston when moving theretoward and said cushioning meansincluding a longitudinal bore having one end thereof opposed to thepiston, a valve plunger means including a valve plunger slidable in saidbore: and a spring for constantly tending to project the inner end ofthe plunger a predetermined distance from the bore in position forengagement by the piston, a duct traversing said bore and communicatingbetween said chamber and the particular cylinder end porting, means forbleeding.

plunger and in the cylinder between said one closure and the piston.

3. The combination of claim 1 wherein the pressure bleeding meanscomprises chamber space behind the plunger and a bleed passage extendingthrough the valve plunger and each end thereof.

4. The combination of claim 1 wherein the cross clearance in the valveplunger comprises an annular groove formed in the plunger exterior.

5. The combination of claim 1 wherein the pressure bleeding meanscomprises chamber space behind the plunger and a bleed passage extendingthrough the valve plunger between the ends thereof, and a cross groovetraversing the piston opposing end of the plunger and disposed toprovide cross clearance when the piston is against the plunger.

6. The combination of claim 1 wherein the pressure bleeding meanscomprises chamber space behind the plunger and a bleed passage extendingthrough the valve plunger between the ends thereof, and a cross groovetraversing the piston opposing end of the plunger and disposed toprovide cross clearance when the piston is against the plunger, saidchamber space being defined in part by a removable plug mounted in saidone closure and providing a back up for the spring and an access openingthrough which the plunger may be serviced,

7. The combination of claim 1 wherein the cross clearance in the valveplunger comprises an annular groove formed in the plunger exterior, andthere is also included means limiting projection of the plunger from thebore in which it is mounted a t't'hepoint at which said annular grooveis in register with the bore traversing duct.

8. The combination of claim 1 wherein said spring alone 4 provides themeans for returning said plunger .to its in'- ward position wherein saidduct is in communication with said bore.

9. The combination of claim 1 wherein said cylinder is of the doubleacting type having substantially identical cushioning means at each ofits ends, each of said cushioning means being associated with anadjacent face of said piston.

References Cited UNITED STATES PATENTS P. E. MASLOUSKY, AssistantExaminer.

8/1960 Flick 91275

1. A PRESSURE CYLINDER HAVING END CLOSURES, PRESSURE FLUID INLET ANDOUTLET PORTING AT THE ENDS THEREOF AND A PISTON RECIPROCABLE THEREINBETWEEN SAID CLOSURES, AND A TERMINAL STROKE CUSHIONING MEANS IN AT LEATONE OF SAID CLOSURES FOR CUSHIONING TERMINAL STROKE MOVEMENT OF THEPISTON THERETOWARD, SAID ONE CLOSURE HAVING A PRESSURE CHAMBER THEREININ WHICH TO RECEIVE PRESSURE FLUID IN ADVANCE OF THE PISTON WHEN MOVINGTHERETOWARD AND SAID CUSHIONING MEANS INCLUDING A LONGITUDINAL BOREHAVING ONE END THEREOF OPPOSED TO THE PISTON, A VALVE PLUNGER MEANSINCLUDING A VALVE PLUNGER SLIDABLE IN SAID BORE AND A SPRING FORCONSTANTLY TENDING TO PROJECT THE INNER END OF THE PLUNGER APREDETERMINED DISTANCE FROM THE BORE IN POSITION FOR ENGAGEMENT BY THEPISTON, A DUCT TRAVERSING SAID BORE AND COMMUNICATING BETWEEN SAIDCHAMBER AND THE PARTICULAR CYLINDER END PORTING, MEANS FOR BLEEDINGPRESSURE FLUID FROM THE BORE FROM BEHIND THE PLUNGER BACK INTO THECYLINDER, AND A CROSS CLEARANCE IN THE PLUNGER PLACED TO AFFORDCOMMUNICATION OF PRESSURE FLUID FROM SAID CHAMBER TO SAID PARTICULARCYLINDER PORTING AND PRESENTING SHOULDER MEANS FOR THROTTLING SAIDCOMMUNICATION AS THE PISTON ENGAGES AND MOVES THE PLUNGER OUTWARD FROMITS INWARDLY PROJECTED POSITION.